A micron is a small unit of measurement that measures length. It is another name for "micrometer," which is one thousandth of a millimeter, or one millionth of a meter. An object that is only a single micron wide is not visible by the human eye. However, a human hair, which has a width around 50 micron, can been seen.
Microns are used in many industries, such as biology (e.g., to measure cell size) and chemical engineering (e.g., to measure particle filtration). They are also used in computing to measure the size of elements within integrated circuits and other components. Additionally, manufacturing specifications may state the dimensions of a product must fall within a certain micron number to meet quality control standards.
While a micron is extremely small, it is still too large to measure some computing components such as transistors and bus widths. These are often measured in nanometers, which are one thousandth of a micron, or one billionth of a meter.
NOTE: The term "micron" used is in both singular and plural cases. For example, one micron is half the length of two micron. While the term "micron" is still used in some industries, micrometers have become a more standard unit of measurement.